Theoretical Study of the Photochemistry of a Reversible Three‐State Bis‐Thiaxanthylidene Molecular Switch

Abstract

The ground- and the lowest singlet excited-state potential energy surfaces of the bis-thiaxanthylidene (3) molecular switch are investigated using a density functional method specifically designed to treat molecular systems typified by strong non-dynamic electron correlation. The results of the theoretical calculations suggest that the unique ability of substituted bis-thiaxanthylidenes to switch between three states of luminescence-non-fluorescent state, blue fluorescent state, and red fluorescent state-can be explained by specific features on the excited state potential energy surface: the potential barrier around the Franck-Condon point of the anti-folded conformer and the existence of conical intersection in the vicinity of the syn-folded conformer. It is suggested that the twisted conformer, if made more stable via chemical modification, should fluoresce in the near-infrared region (λ≈740-760 nm), thus offering a possibility for a four-state switching of luminescence in a single-component molecular system.

Machine Learning-Assisted Excited State Molecular Dynamics with the State-Interaction State-Averaged Spin-Restricted Ensemble-Referenced Kohn–Sham Approach

“…The SSR­(2,2) method is suitable for describing nearly degenerate KS systems such as CIs, and many applications have been done so far to describe photochemical reactions with the n – π* and π – π* transitions. − Although SSR­(2,2) is limited to calculation of only the lowest two singlet states, the general extension of SSR is quite straightforward. The formulation of SSR­(4,4) is also available, which is suitable to describe dissociation of multiple bonds.…”

Photoredox C(sp3)−C(sp3) Cross‐Dehydrogenative Coupling of Xanthene with β‐keto Moiety using MoS2 Quantum Dot (QD) Catalyst.

“…Functionalized xanthene motif exhibits a wide range of activity in biological and material sciences [30–34] (Figure 1). Because of prevalence of xanthene motif, many synthetic methodologies have been developed for their functionalization, one of them is via CDC approach (Scheme 1).…”

“…[18][19][20][21][22][23][24][25][26] Nevertheless, most of the photoredox catalysts are either expensive Ir, Ru transition metal based or environmentally unpropitious larger organic molecules. [27][28][29] Functionalized xanthene motif exhibits a wide range of activity in biological and material sciences [30][31][32][33][34] (Figure 1). Because of prevalence of xanthene motif, many synthetic methodologies have been developed for their functionalization, one of them is via CDC approach (Scheme 1).…”

Spin‐restricted ensemble‐referenced Kohn–Sham method: basic principles and application to strongly correlated ground and excited states of molecules

“…In the past, the REKS method has been successfully applied to investigate the electronic structure of strongly correlated molecular systems, such as the low‐spin states of biradicals, magnetically coupled metal centers, organic charge transfer salts . Later, the method has been extended to treat excited states of strongly correlated molecular species and the resulting state‐averaged REKS (SA‐REKS) and state interaction SA‐REKS (SI‐SA‐REKS) methods have been used to investigate the photochemistry of molecular motors and molecular switches, to study the excited states of extended π ‐conjugated molecules, and to investigate peculiarities of the excited state charge transfer in donor–acceptor systems . Although the REKS method has demonstrated its feasibility and ability to accurately describe fine detail of the electronic structure of strongly correlated molecular species, its theoretical background and practical implementation seem to be little known by the computational chemistry community at large.…”